Electrolytic cell for producing charged anode water suitable for surface cleaning or treatment, and method for producing the same and use of the same

ABSTRACT

The present invention provides an electrolytic cell, which can efficiently produce, charged water having an excellent performance of improving surface cleaning or treatment of an object, e.g., semiconductor, glass, or resin and of cleaning and sterilizing medical device.  
     The electrolytic cell of the present invention is for producing charged anode water suitable for surface cleaning or treatment, including the cathode chamber  41  and anode chamber  50,  fluorinated cation-exchange membrane  46  provided to separated these chambers from each other, cathode  44  closely attaché to the cation-exchange membrane  45  on the side facing the cathode chamber  41,  and middle chamber  48  filled with the cation-exchange resin  46,  provided on the other side of The cation-exchange membrane  46,  the cation-exchange resin  46  being arranged in such a way to come into contact with the fluorinated cation-exchange membrane  45,  wherein the feed water is passed into the middle chamber  48  and passed thorough The anode chamber  50  to be recovered as the charged anode water.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention is related to a method for surface cleaningor treatment of semiconductors, glass, or resins, and device forproducing electrically charged water as utility water for the abovemethods, more particularly a technique for providing an electrolysiscell, which can produce electrically charged water suitable for surfacecleaning or treatment without using chemical in consideration ofenvironmental protection. The electrically charged water produced byusing the electrolysis cell also has antimicrobial activates, and issuitable for cleaning and sterilizing medical devices for which highcleanliness is required.

[0003] 2. Description of the Related Art

[0004] Electrolysis cell using ion exchange membrane, as shown FIG. 1,facilitates the electrolysis of water with low conductivity such as ROwater treated using a reverse osmosis membrane pure water, and ultrapure water. In this cell, a fluorinated cation exchange membrane 5 isusually used.

[0005] And then an anode electrode 4 in the anode cell 1 and a cathodeelectrode 9 in the cathode cell 6 are closely attached to the membrane5. The notation 2 denotes the anode chamber inlet, 3 denotes anodechamber outlet, 7 denotes the cathode chamber inlet, and 8 denotes thecathode chamber outlet.

[0006] The ion exchange group in fluorinated cation exchange membrane 5shown in FIG. 1 is known to enhance the dissociation even in the purewater according to the reaction (1).

—SO₃H→—SO₃ ⁻+H⁺  (1)

[0007] The dissociated hydrogen ions increase the electro conductivityof pure water, which contains no impurities, and then decrease theelectrolysis voltage.

[0008] Next, the reaction (2) and (3) proceed when pure water iselectrolyzed using the cell shown in FIG. 1.

[0009] At anode

2H₂O→2H⁺+O₂+2e⁻  (2)

[0010] At cathode

2H⁺+2e⁻→H₂  (3)

[0011] These reactions increase the oxygen concentration in the anodesolution and the hydrogen concentration in the cathode solution, whilesare leaving the essential properties of electrolytic water unchanged.

[0012] In other words, the charged water produced using electrolysiscell shown in FIG. 1 may not be suitable for the surface cleaning ortreatment of semiconductors, glass, or resins.

[0013] In order to enhance the cleaning or surface treatment efficacy,anode water is required to be more oxidative and/or acidic and cathodewater is required to be more reductive and/or alkaline. However, theelectrolysis cell shown in FIG. 1 is difficult to produce the effectivesolutions.

[0014] For example, the oxidation and reduction potential (hereinafterabbreviated as ORP) of anode water is from 200 to 300 mV (vs., Ag/AgCl)and pH is around neutral: the ORP of normal pure water is around 200 mV.

[0015] The three-chamber cell shown in FIG. 2 is designed to solve theproblem mentioned above, where the middle chamber 111 is added betweenthe anode chamber 11 and the cathode chamber. 16. Using thethree-chamber cell easily electrolyzes pure water or ultra pure water.

[0016] Referring to FIG. 2, the three-chamber cell has the chamber 11and 111 separated by the ion exchange membrane 151, chamber 16 and 111separated by the ion exchange membrane 152, the middle chamber 111filled with ion exchange resins as a solid electrolyte, the middlechamber inlet 112 and outlet 113, cathode 19 and anode 14 provided insuchaway to be closely attached to the ion exchange membrane 151 and152, respectively, the anode camber inlet 12 and outlet 13, and thecathode chamber inlet 15 and 17.

[0017] The three-chamber cell has the following merits. Reductivespecies such as dissolved hydrogen gas produced in the cathode chamber16 are likely to migrate into the anode chamber 11 though the ionexchange membrane 5 when the cell depicted in FIG. 1 is used. However,the middle chamber 111 in the three-chamber cell control the diffusionof reductive species from the cathode chamber 16 to the anode chamber 11and then the more strongly oxidative anode water can be obtained. In thecell shown in FIG. 2, migration of hydrogen ions formed on the anode 14toward the cathode 19 is limited, and then the electrolysis reaction (4)takes place in addition to the reaction (3):

H₂O+2e⁻→½H₂+OH⁻  (4)

[0018] This reaction suggests that the pH of cathode water tends toshift to the alkaline region.

[0019] In another viewpoint, these phenomena suggest that hydrogen ionsformed in the anode chamber 11 in the reaction (1) remain partly in thatchamber.

[0020] In the three-chamber cell shown in FIG. 2 the anode solution,therefore, is likely to be charged with the hydrogen ions, whiles thecathode water is charged with hydroxide ions.

[0021] Electrochemical analytical methods are suitable for monitoringcharges or the like to experimentally confirm the phenomena mentionedabove. For example, the changes in measured values can be monitored by apH sensor equipped with a glass electrode or ORP sensor which measurethe oxidation-reduction potential of platinum electrode surface as astandard of a silver/silver chloride electrode. These sensors, followingpotential changes in the electrodes as the index, are suitable forconfirming charges of electrolytic water. A temperature of theelectrolytic water is usually kept at from 18 to 24° C. duringmeasurement (the temperature in the following examples was kept at thealmost same levels).

SUMMARY OF THE INVENTION

[0022] The charged electrolytic water produced using pure waterfunctions as cleaning/surface treatment reagents for semiconductors,liquid crystal glass and hard disk glass or cleaning/sterilizingreagents for medical devices. A decontamination mechanism usingelectrolytic solutions is simply explained as follows.

[0023] Some contaminants are adhered to the surface of the devicementioned above by electrostatic or ionic attractive forces asschematically shown in FIG. 3, where (A) indicates the contaminatedsurface and (B) indicates the cleaned surface: the surface of substrateis supposed to be positively charged and contaminants are supposed to benegatively charged. When the contaminated substance is immersed in theeffectively charged anode water, the negatively charges on thecontaminants surface reacts with excess hydrogen ions in the anodewater. Thus the surface charges are partly neutralized to reduce thebonding forces and thereby to facilitate cleaning. Conversely, when thecontaminants are positively charged, the negative charges on thecontaminated substance surface disappear to reduce the bonding forces.On the other hand, in the case of ionic contaminants, when thecontaminated substance is immersed in anode water with excessivehydrogen ions, the anionic contaminants on the surface are likely todissolve and then migrate to the anode solution to cancel the excessivecharge. Using electrolytic water increases thus cleaning efficacy.

[0024] Anodic electrolysis of pure water produces the hydrogen ionsaccording to the reaction (2), where no anion is present as counter ion,unlike acidic solutions prepared by adding acid such as hydrochloricacid or sulfuric acid. The anode water produced by electrolyzing purewater exhibits that the solution is charged. Moreover, the hydrogen ionby itself is an electron acceptor and so exhibits one of oxidizingspecies. So, the oxidation-reduction potential of anode water tends toshift to noble side. In other words, the ORP sensor indicates a plusvalue.

[0025] When the three-chamber cell depicted in FIG. 2 is used, the anodewater is not necessarily sufficient for actual cleaning or surfacetreatment, although the theoretical consideration mentioned aboveappears to be very promising. So improving the cell is very important toapply to actual use.

[0026] More specifically, the important factors for producing effectivecharged water are an apparent current density (current (A)/apparent areaof whole electrode (cm²), a fluid velocity along the electrode surface,and an true current density (effective current density=current (A)/truearea of the electrode (cm²)). As the fluid velocity increases, thehydrogen ions and other electrolytic species produced on the electrodesurface migrate faster to electrolytic water and then strangely chargedwater can be produced.

[0027] The inventors of this invention have found that it is importantto pass water not only over the back side of electrode but also over thefront side of electrode, based on the study to improve charged waterproduction efficacy.

[0028] This result has led to the development of new methods forimproving surface cleaning or treatment performance in semiconductors,glass, resins or the like, and of the apparatus (electrolytic cell) ofthe present invention which can efficiently produce the charged waterwith an excellent performance described above.

[0029] The invention has the following characteristic constituents toachieve the above objects.

[0030] (1) An electrolytic cell for producing charged anode watersuitable for surface cleaning or treatment, including cathode, middleand anode chambers, a fluorinated cation-exchange membrane provided toseparate cathode and middle chambers from each other, A cathode closelyattached to the cation-exchange membrane on the side facing the cathodechamber, and a middle chamber filled with fluorinated cation-exchangeresins, provided on the other side of the cation-exchange membrane, thecation-exchange resins being arranged in such a way to come into contactwith the fluorinated cation-exchange membrane in the cathode chamberside and with the anode in the anode chamber side, wherein the feedwater is fed into the middle chamber and passed through the fluorinatedcation-exchange resins to be recovered as the charged anode water.

[0031] A shape of the fluorinated cation-exchange resin in thisinvention is not limited. It may be granular or fibrous, the formerbeing more preferable.

[0032] The term “surface cleaning” used in this specification means anoperation to remove contaminants from the surface and “surfacetreatment” means an operation to change surface composition or the likeof a substance, e.g., glass, having ions, e.g., Na⁺, K⁺, and H⁺, bondedin the bonding network of Si—O. Phenomena of the migration of Na⁺ ionsin glass were observed. When Na⁺ ions present in the vicinity of thesurface are removed, or more specifically ion-exchanged on the surface,the surface is prevented from roughing caused by the Na⁺ ions. Thisprocess means the surface treatment, which is different form, theremoval of foreign particles or impurity ions form the surface.

[0033] The ion-exchange membrane is usually cation-exchange membrane,preferably fluorinated cation-exchange membrane. It is essential for thepresent invention that the anode to be used in combination with theion-exchange resins (cation-exchange resins) is a porous electrode orelectrode having an ineffective area.

[0034] (2) The electrolytic cell for producing charged anode watersuitable to surface cleaning or treatment according to the invention(1), wherein a porous anode is provided, and the middle chamber has aninlet but no outlet for the feed water to be treated and the anodechamber has an outlet for treated water but no inlet for the feed water.

[0035] (3) An electrolytic cell for producing charged anode water forsurface cleaning or treatment, including cathode, middle and anodechambers, a fluorinated cation-exchange membrane provided to separatethe cathode and middle chambers form each other, cathode closelyattached to the cation-exchange membrane on the side facing the cathodechamber, cation exchange resins contained in the middle chamber andarranged to come into contact with the cation-exchange membrane on theopposite side facing the middle chamber. another fluorinatedcation-exchange resins contained in the compartment between thefluorinated cation exchange membrane and the anode, wherein the feedwater is passed over the anode surface and electrolytic water dischargedfrom the anode chamber is recovered as the charged anode water.

[0036] (4) The electrolytic cell for producing charged anode watersuitable for surface cleaning or treatment according to the invention(3), wherein a cation-exchange membrane is arranged in the middlechamber to divide the chamber into first middle chamber on the cathodechamber side and a second middle chamber on the anode chamber side.

[0037] (5) The electrolytic cell for producing charged anode watersuitable for surface cleaning or treatment according to one of theinventions (1) to (4), whereon holes in the porous anode have a totalarea of 10% or more of a whole electrode area.

[0038] The holes are preferably arranged evenly on the entire electrodeplane. Each hole preferably has an area of 1 mm² or more inconsideration of passing efficiency of the anode water.

[0039] The anode for the present invention preferably has holes havingan area 1 mm² or more, because a granular cation-exchange resin, whenused, tends to pass through the holes, as its diameter is generally 1 mmor so, frequently 2 to 4 mm. However, a porous electrode having a largehole area is serviceable for a resin, e.g., fluorinated cation-exchangeresins, which swell in pure water to have a higher friction coefficientbetween theres in particles. More specifically, DuPont' Nafion NR50 ispreferable resin. A fluorinated one is preferable in consideration ofresistance of the cation-exchange resin to oxidation reaction. Morespecifically, Du Pont' Nafion NR50 is preferable resin

[0040] (6) The electrolytic cell for producing charged anode watersuitable for surface cleaning or treatment according to one of theinventions (1) to (4), wherein the electrode has an ineffective area,which has no contribution to electrolysis, of 10% or more of the wholeelectrode area.

[0041] (7) The electrolytic cell fro producing charged anode watersuitable for surface cleaning or treatment according to one of theinventions (1) to (6), wherein a mechanism of controlling position ofthe anode in the direction of current flowing towards to cation-exchangeresin is provided.

[0042] (8) The electrolytic cell for producing charged anode watersuitable for surface cleaning or treatment according to one of theinventions (1) to (7), wherein the cation exchange resin is fluorinatedone.

[0043] (9) A method of using charged anode solution produced by theelectrolytic cell according to one of the inventions (1) to (8) forsurface cleaning or treatment of an object.

[0044] (10) A method using charged anode water produced by theelectrolytic cell according to the inventions (1) to (9), wherein feedwater is pure water or ultra pure water. Pure water or ultra pure watermeans water having the resistivity of 0.1MΩ/cm or more.

[0045] (11) The method using charged anode water according to theinvention (10), wherein the object to be cleaned or treated is asemiconductor, glass, or resin product.

[0046] (12) A method using charged anode water according to theinvention (10), wherein the object to be cleaned or treated is a medicaldevice.

[0047] (13) A method using charged anode solution produced by theelectrolytic cell according to one of the inventions (1) to (9), whereinthe feed water to the anode chamber is cooled to increase the ozoneconcentration in the anode water.

[0048] (14) A method using charged anode water produced by theelectrolytic cell according to one of the inventions (1) to (4), (6) and(8) to (12), wherein the anode is directly cooled to increase the ozoneconcentration in the charged anode water.

[0049] The porous anode or cathode in each aspect of the presentinvention described above means that the planar electrode is structuredto have holes (hereinafter referred to as “opening”) through which watercan pass on both front and backside. These openings are preferablyarranged in such a way to make resistance to water flow uniformthroughout the plane, and normally distributed evenly on the plane.Adequate size of the opening and ratio of the total opening area to thewhole planar electrode area changes depending on the current density andresistance to water flow so that the apparatus is required to secure,and are not determined sweepingly.

[0050] These factors greatly depend on the electrode hole structure andion-exchange resin size: increasing opening size and/or ion-exchangeresin size decreases the resistance to water flow and, at the same time,increases the effective current density because contact area between theelectrode and resins decreases. However, it is difficult to hold theion-exchange resins between the membrane and electrode, when openingsize increases excessively. Therefore, there is an optimum shape foreach of opening and ion-exchange resin.

[0051] As discussed above, the electrolytic anode water, produced bypassing pure water through the electrolysis cell having a controllingfunction, has the characteristics described in the examples.

BRIEF DESCRIPTION OF THE DRAWINGS

[0052]FIG. 1 shows the schematic cross-sectional view of theconventional electrolytic cell for electrolysis using ion-exchangeseparator.

[0053]FIG. 2 shows the schematic cross-sectional view of theconventional three-chamber type electrolytic cell.

[0054]FIG. 3 describes the decontamination mechanism using theelectrolytic water, where (A) describe the situation before treatmentand (B) that after treatment.

[0055]FIG. 4 shows the schematic cross-sectional view of theelectrolytic cell in the first embodiment of the present invention.

[0056]FIG. 5 shows the schematic cross-sectional view of theelectrolytic cell in the second embodiment of the present invention.

[0057]FIG. 6 shows the schematic cross-sectional view of theelectrolytic cell in the third embodiment of the present invention.

[0058]FIG. 7 shows the influence of the area ratio on pH and ORP valuesof the electrolytic anode water prepared in the example 1.

[0059]FIG. 8 shows the influence of electrolytic current on pH and ORPvalues of the electrolytic anode water prepared in the example 2.

[0060]FIG. 9 shows the influence of the anode position on chargingcharacteristics of the anode water prepared in the example 3.

[0061]FIG. 10 shows the relationship between removal rate and cleaningtime obtained in the example 4.

[0062]FIG. 11 shows the Na⁺ ion distribution in the depth directionbefore and after the treatment, observed in Example 6.

[0063]FIG. 12 shows the relationship between the number of bacteria andthe contact time with electrolytic anode water prepared in the example7.

[0064]FIG. 13 shows the relationship between the number of bacteria andORP of the electrolytic anode water prepared in the example 7.

[0065]FIG. 14 shows the electrolytic cell system in which a cooler isbuilt.

[0066]FIG. 15 shows the electrolytic cell system in which a cooler isbuilt.

[0067]FIG. 16 shows the relationship between the ozone concentration andtemperature in the middle chamber obtained in the example 8.

[0068]FIG. 17 shows the schematic cross-sectional view of theelectrolytic cell in which a cooling chamber is built, described in theexample 9.

[0069]FIG. 18 shows the schematics of a PTFE sheet.

[0070]FIG. 19 shows the system diagram of the electrolytic cell in whicha cooling chamber is built.

DETAILED DESCRIPTION OF THE REFERRED EMBODIMENTS

[0071] The three-chamber type electrolytic cell to which the presentinvention is applied is described as follows.

[0072] Embodiment 1

[0073]FIG. 4 illustrates the new three-chamber type electrolytic cellmade by improving the conventional three-chamber cell in which theperforated electrode plate shown in the drawing is used.

[0074] The anode 53 was closely attached to the cation-exchange membranebefore the improvement. Therefore, the electrolytic water flowed alongthe anode plane, and the electrolysis reaction proceeded between theelectrode and ion exchange membrane. As a result, the electrolysisproducts were formed first between the electrode and ion exchangemembrane, and then moved toward the backside of electrode by diffusionor the like.

[0075] In the present invention, on the other hand, the anode isperforated to provide the passages for electrolytic water passing overthe electrode surface, in order to utilize the electrolysis product moreefficiently. As a result, the electrolytic water flows not only on theelectrode surface but also thorough the holes opened in the electrode.The relationship between opening size and ion-exchange resin size isvery important. It is necessary to increase the opening size ofelectrode, in order to water flow rate. However, it is difficult to holdthe ion-exchange resins between the membrane and electrode, when theopening size increases excessively as compared with ion-exchange resinsize. The ion-exchange resin is either spherical or fibrous, the formerbeing generally more preferable. Its diameter is ranging from around 1mm when it is small to 2 to 4 mm when it is large. Therefore, anexcessively large opening size in comparison with ion-exchange resins isundesirable. The ion-exchange resin preferably has a large diameter toreduce resistance to water flow. Moreover, the fluorinatedcation-exchange resin is preferable, because it comes into contact withthe anode.

[0076] Moreover, the fluorinated cation exchange resins greatly decreasethe electrolysis voltage and thus facilitate the electrolysis of purewater. The Nafion NR50 made by Du Pont is preferable fluorinatedcation-exchange resin, as mentioned earlier.

[0077] It is possible to control the current density by changing thecontact area between the fluorinated cation-exchange resin and anode.The fluorinated cation-exchange resin naturally swells in pure water. Soits diameter increases with swelling and the swelling increases withtemperature. As a result, the contact area between the fluorinatedcation-exchange resin and electrode varies with ambient conditions. Itis therefore necessary to control the contact area, in order to controlthe current density.

[0078] The electrolytic cell shown in FIG. 4 has a characteristicstructure suitable for surface cleaning or treatment. The cell includesthe cathode chamber 41, middle chamber 48 and anode chamber 50,fluorinated cation-exchange membrane 45 provided to separate the cathodechamber 41 and middle chamber 48 from each other, cathode 44 closelyattached to the cation-exchange membrane 45 on the side facing thecathode chamber 41, cation exchange resin 46 contained in the middlechamber 48 and arranged to come into contact with the cation-exchangemembrane 45 on the opposite side facing the middle chamber 48,cation-exchange membrane 54 provided between the middle chamber 48 andanode chamber 50, wherein the feedwater is passed through the anodechamber 50 and the produced electrolytic water discharged from the anodechamber 50 is recovered as the charged anode water. The other componentsof the electrolytic cell shown in FIG. 4 are the cathode chamber inlet42, cathode chamber outlet 43, middle chamber inlet 47, middle chamberoutlet 49, anode chamber inlet 51 and anode chamber outlet 52.

[0079] Embodiment 2

[0080] The electrolytic cell shown in FIG. 5 has a characteristicstructure in that the feed water flows into the middle chamber 46 andthe electrolyzed water discharged from the anode chamber 50 is recoveredas the charged anode water. The cell structure as those shown in FIG. 4are given the same number and their descriptions is omitted.

[0081] Embodiment 3

[0082] The electrolytic cell structure includes a mechanism to adjustthe position of anode 53 in the current flowing direction, as shown inFIG. 6. This structure is provided with a frame, outside of the cell,which holds the mobile anode position-adjusting mechanism.

[0083] The anode position adjusting mechanism typically is composed ofan anode-supporting rod provided with a screw, by which the anodeposition can be adjusted.

[0084] The structure is described in more detail. This structure makesit possible to adjust position of the anode 53, shown in FIG. 4 forembodiment 1, in the current passing direction. More specifically, theanode-supporting rod 58 is set at approximately center of the anode 53in the current passing direction, held by the holding frame 57 providedin the anode chamber 50 in such a way to be movable in the axialdirection, and screwed into the position-adjusting mechanism 56,provided outside of cell, via the O-ring 55 which seals theanode-supporting rod 58. The position can be adjusted by cutting theanode-supporting rod 58 to have male threads and the position-adjustingmechanism 56 to have the corresponding female threads. Position of theanode 53 is adjusted by rotating the position-adjusting mechanism 56 tocontrol the effective electrolysis current. This means the increase inthe electrolysis voltage. Detaching the anode 53 from the cathode sideimproves charging characteristics of the cell.

[0085] The same components as those describe in embodiment 1 are giventhe same numbers and their descriptions are omitted.

EXAMPLES Example 1

[0086] The three-chamber type electrolytic cell shown in FIG. 4 wasused, where ultra pure water was supplied to the inlets of the anodechamber 50, middle chamber 48 and cathode chamber 41. The ultra purewater had the following properties:

[0087] Resistively; 18.0 MΩ/cm

[0088] Water temperature: 15° C.

[0089] Opening diameter: 4φ

[0090] Electrode: Platinum plated titanium electrode was used.

[0091] Ion-exchange membrane: The membrane 45 was made of a fluorinatedcation-exchange membrane (Nafion 117 made by Du Pont)

[0092] Ion exchange resin filled in the middle chamber: The middlechamber 48 was filled with a granular fluorinated cation-exchange resin(Nafion NR50 made by Du Pont).

[0093] Ion exchange filled in the anode chamber: the room between theanode 53 and membrane 45 was also filled with NR50.

[0094] Water flow rate: ultra pure water was passed at 0.75 l/min.through the cathode chamber 41 and anode chamber 50.

[0095] The perforated anode 53 assembled in the electrolytic cell usedin the example 1 had an apparent area of 48 cm².

[0096] The apparent area of the electrode (the openings weretwo-dimensionally evenly arranged in the Example 1 as follows.

[0097] Electrode thickness; 1 mm

[0098] Total opening area: 16.23 cm²

[0099] Opening ratio; 34%

[0100] The ratio of the opening area to the apparent electrode area waschanged to obtain the relationship between the ratio and the pH and ORPof charged anode water where the apparent electrolytic current was setat 5 A, as shown in FIG. 7. The electrolysis voltage was very low andaround 14 v under this condition. As clear from the figure, measured pHand ORP values, which are characteristic of the anode water, are verysensitive to the area ratio.

Example 2

[0101] The effects of electrolytic current on characteristics of anodewater were investigated using the same electrolytic cell and ultra purewater as those use in the example 1. FIG. 8 shows the effects ofelectrolytic current on pH and ORP of the anode water. The chargingcharacteristics such as pH and ORP were improved as the current densitywas increased.

Example 3

[0102] The electrolytic cell with adjusting function of anode positionshown in FIG. 6 was used to investigate the relationship between theanode electrode position and the charging characteristics such as pH andORP of anode water, where apparent electrolytic current was set at 4 A.FIG. 9 indicates the result.

[0103] The minus position of anode in FIG. 9 indicates that the anodeapproached towards the cathode side. In order set the electrolyticcurrent at a given level, the electrolytic voltage was decreased, as theanode position was moved toward the cathode side. As the position ofanode was moved toward the counter side, the charging characteristicssuch as pH and ORP were improved. These results shows that the effectivecontact area between the cation exchange resins and anode decreases asthe anode is move towards the counter side. The fluorinated ion exchangeresin used in the example 3 had rubber like elasticity and was capableof reversibly changing the charging characteristics.

Example 4

[0104] In this example, the anode water was used to confirm the cleaningefficiency. The object to be cleaned was polyethylene plate on which aprinting paint (base material was an acrylic resin) containing carbonblack was spread. The electrolytic cell was the same one as that used inthe example 1, where ultra pure water was supplied to each chamber atthe flow rate of 0.75 l/min, and electrolytic current was set at 7A. Theanode water thus produced was run at the same flow rate on the surfaceof the polyethylene plate for cleaning. FIG. 10 shows the cleaningefficacy, which was defined as the difference between the object weightbefore and after cleaning divided by the weight before cleaning. Forcomparison, the ultra pure water without electrolysis was used forcleaning the plate. FIG. 10 indicates that anode solution exhibits ahigher cleaning efficacy.

Example 5

[0105] Next, the effects of anode water on the removal rate of fineparticles on silicon wafer were investigated. First, the 8-inch barewafer was placed on rubber to contaminate with fine particles thereon.The number of fine particles adhered to the wafer surface was rangingfrom 2,000 to 4,000. Then, The wafer was washed with the electrolyticanode water, which was produced under the same condition as in theexample 1, where the electrolytic current was se at 5 A. Theelectrolytic water was kept in a PFA bottle (20 l), from which the waterwas run onto the wafer at the flow rate of 3 l/min using a diaphragmpump. The overall schedule is described as follows.

[0106] Cleaning with ultra pure water (2 minutes)→cleaning withelectrolytic water (3 minutes)→drying by using s spin drier (2 minutes).

[0107] The silicon wafer was also cleaned with ultra pure water in placeof the electrolytic water for comparison. Table 1 shows the cleaningresults. TABLE 1 removal pH ORP rate total (%) 6.8 430 31.5 6.5 460 46.36.2 510 60.8 5.9 680 89.0 5.5 720 99.5

Example 6

[0108] In this example, glass substrates for hard disks were treatedwith electrolytic water.

[0109] When a hard disk glass was immersed in the anode water, thesurface compositions of hard disk glass were found to change. This glasscontained cation such as Na⁺, K⁺, and H⁺, bonded in the bonding networkof Si—O.

[0110] Sodium ions is known to damage the surface and so desired toremove from surface region to prevent surface roughing. In order toconfirm the possibility of ion exchanging effects in anode solution,glass was immersed in the anode water and then the depth profile ofcation distribution in a surface layer was measured.

[0111] The charged water was produced by using the same electrolyticcell as use in the example 1, where electrolytic current was set at 5 A.The glass was immersed in the charged anode solution for 5 minutes, toobserve the surface composition by using an Auger analyzer. FIG. 11shows the Na⁺ ion distribution in the depth direction before and afterimmersion. As shown in FIG. 11, immersing the glass in the anodesolution decreases the Na⁺ ion concentration in the surface layer.

Example 7

[0112] The antimicrobial activities of anode water were investigatedusing the electrolytic cell of present invention. The anode water wasproduced by using the same cell as used in the example 1, whereelectrolytic current was set at 8 A. A bacteria containing solution wasprepared, where the number of Escherichia coli was adjusted to around107. One part of the bacteria-containing solution was mixed with 30parts of the anode solution. The mixture, stirred for a give time, wasspread on the standard agar culture medium to culture the bacteria at30° C. for 24 hours and the number of the bacteria was countered. FIG.12 shows the relationship between the number of bacteria and the contacttime with the anode water. FIG. 13 sows the sterilization effect of theanode water, where the number of bacteria is plotted against ORP of thewater. FIG. 12 and 13 indicates that the anode water exhibits thesterilization effect when the ORP level exceed 800 mV.

Example 8

[0113] Oxidation capacity of the anode solution produced by anelectrolytic cell is also very sensitive to electrolysis temperature. Asthe temperature decreases, the ozone production efficacy increases andthen the oxidation capacity increases. Cooling is a good method fordecreasing the temperature in the electrolytic cell. The cooling systemdepicted in FIG. 14 and 15 can keep temperature of water in a middlechamber or cathode chamber at low level, to improve ozone productionefficiency. FIG. 16 shows that the ozone production efficiency changeswith temperate in electrolytic cell used in the example 1 with thecooling system shown in FIG. 14. In FIG. 14 and 15, same components asthose described in embodiments are given the same numbers and theirdescriptions are omitted. The other components are the three-chambertype electrolytic cell 60, cooler 61, anode electrolytic water tank 62,feed water line 63 and pump 64.

Example 9

[0114] The example 9 describes another cooling method. As depicted inFIG. 17, the anode chamber is divided into the camber through which theanode water flows and the other chamber through which cooling waterflows. In FIG. 17, the same components as those described in theembodiment 1 are given the same numbers and their descriptions areomitted. The other components are the cooling chamber inlet 66, coolingchamber outlet 65, cooling chamber 67 and baffle 68.

[0115] In this case, the anode was not provided with openings. However,a perforated PTFE (fluorocarbon resin) shown in FIG. 18 was placed on asurface of the anode of platinum-plated titanium, 80 by 60 mm, toincrease effective current density on the anode. In this example, thePTFE sheet, 60 by 80 mm, was provided with openings of 4 mm in diameter,as shown in FIG. 18.

[0116] Temperature in the electrolytic cell was controlled by the systemshown in FIG. 19, which passed cooling water to cooling chamber todirectly cool the anode. In FIG. 19, the same components as thosedescribed in the embodiment are omitted. The other components includethe liquid tank 69 in the middle chamber. Keeping temperature in theelectrolytic cell at a low level by using the cooler improved ozoneproduction efficiency, as described in the example 8.

[0117] The electrolytic cell of the present invention can producestrongly charged anode water. Moreover, It can improve ozone productionefficiency, when its anode is cooled. The charged water produced by theelectrolytic cell is effective for cleaning a silicon wafer by removingfine particles or the like wherefrom or glass surface treatment forpromoting ion exchanging on the surface to prevent surface roughing. Itis also effective for cleaning resins or the like, in particular resinsfor medical devices. For Example, it is effective for cleaning andsterilizing the inner surfaces of catheters or like. No special chemicalremains after cleaning, which is its advantage.

What is claimed is
 1. An electrolytic cell for producing charged anodewater suitable for surface cleaning or treatment, including cathode,middle and anode chambers, a fluorinated cation-exchange membraneprovided to separate cathode and middle chambers from each other, Acathode closely attached to the cation-exchange membrane on the sidefacing the cathode chamber, and a middle chamber filled with fluorinatedcation-exchange resins, provided on the other side of thecation-exchange membrane, the cation-exchange resins being arranged insuch a way to come into contact with the fluorinated cation-exchangemembrane in the cathode chamber side and with the anode in the anodechamber side, wherein the feed water is fed into the middle chamber andpassed through the fluorinated cation-exchange resins to be recovered asthe charged anode water.
 2. The electrolytic cell for producing chargedanode water suitable for surface cleaning or treatment according toclaim 1, wherein a porous anode is provided, and said middle chamber hasan inlet but no outlet for the feed water to be treated and said anodechamber has an outlet for the treated water but no inlet for the feedwater.
 3. An electrolytic cell for producing charged anode watersuitable for surface cleaning or treatment, including cathode, middleand anode chambers, a fluorinated cation-exchange membrane provided toseparate the cathode and middle chambers form each other, a cathodeclosely attached to the cation-exchange membrane on the side facing thecathode chamber and arranged to come into contact with thecation-exchange membrane on the opposite side facing the middle chamber,another fluorinated cation-exchange membrane provided between the middleand anode chambers, another fluorinated cation-exchange resins containedin the space between the fluorinated cation-exchange membrane and theanode, wherein the pure water is passed over the anode surface andelectrolytic water discharged form the anode chamber is recovered as thecharged anode water.
 4. The electrolytic cell for producing chargedanode water suitable for surface cleaning or treatment according toclaim 3, wherein a fluorinated cation-exchange membrane is arranged insaid middle chamber to divide the chamber into a first middle chamber onthe cathode chamber side and a second middle chamber on the anodechamber side.
 5. The electrolytic cell for producing charged anode watersuitable for surface cleaning or treatment according to any of claims 1to 4, wherein holes in said porous anode have a total area of 10% ormore of a whole electrode area.
 6. The electrolytic cell for producingcharged anode water suitable for surface cleaning or treatment accordingto any of claims 1 to 4, wherein said electrode has an ineffective area,which has no contribution to electrolysis, of 10% or more of the wholeelectrode area.
 7. The electrolytic cell for producing charged anodewater suitable for surface cleaning or treatment according to any ofclaims 1 to 6, wherein a mechanism of controlling position of said anodein the direction of current passing towards said cation-exchange resinsis provided.
 8. The electrolytic cell for producing charged anode watersuitable for surface cleaning or treatment according to any of claims 1to 7, wherein said cation-exchange resin is fluorinated one.
 9. A methodof using charged anode water produced by any of the electrolytic cellsaccording to claims 1 to 8 for surface cleaning or treatment of anobject.
 10. A method of using charged anode water produced by theelectrolytic cell according to any of claims 1 to 9, wherein feed wateris pure water or ultra pure water.
 11. The method of using charged anodewater according to claim 10, wherein said object to be cleaned ortreated is a semiconductor, glass or resin product.
 12. The method ofusing charged anode water according to claim 10, wherein said object tobe cleaned or treated is a medical device.
 13. A method of using chargedanode water produced by the electrolytic cell according to any of claims1 to 5, 7 to 12, wherein said charged anode water is cooled to increaseits ozone concentration.
 14. A method of using charged anode waterproduced by the electrolytic cell according to any of claims 1 to 4, 6and 8 to 12, wherein said anode is directly cooled to increase ozonecontent of the charged anode water.